JP2007015025A - Taper neck end mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the machining quality and to lengthen the life of an end mill by preventing the end mill body from coming into contact with the machined groove wall surface even if bending is a little caused in a cutting blade part in a taper neck end mill including a cutting blade whose rotation locus is cylindrical in parallel to the axis of the end mill body. <P>SOLUTION: In this taper neck end mill, the cutting blade part 13 including the cutting blade 16 whose rotation locus round the axis O is cylindrical round the axis O is formed at the tip part of the end mill body 11 rotated round the axis O, a neck part 14 is formed on the rear end side of the cutting blade part 13, and the neck part 14 is formed of: a taper neck part 20 whose outside diameter gradually increases as it goes toward the rear end side; and a parallel neck part 19 formed between the taper neck part 20 and the cutting blade part 13, having an outside diameter (d) smaller than the outside diameter D of the cutting blade 16 and extending in parallel to the axis O. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tapered neck end mill in which a tapered neck portion whose outer diameter gradually increases toward the rear end side is formed on the rear end side of the cutting edge portion.

  Such a taper neck end mill is used in a deep groove machining of a mold with a long protrusion of the end mill's cutting edge, and the neck portion on the rear end side of the cutting edge is entirely aligned with the axis of the end mill body. Compared to a long neck end mill that has a parallel long shaft, the outer diameter of the neck part on the rear end side (shank side) of the end mill body can be increased, so the rigidity of this neck part is large, and bending during cutting is possible. Can be suppressed.

As this type of taper neck end mill, for example, in Patent Documents 1 and 2, the cutting edge portion has a tapered shape, and the rear end side thereof has a taper angle substantially equal to that of the cutting edge portion and has a slightly narrow diameter. Some have been proposed with a neck that is part of a cone. In Patent Documents 3 and 4, the length under the neck of the end mill body is set to 10 times or more of the cutting edge diameter. However, Patent Document 4 proposes a technique in which the surface roughness in the vicinity of the joint portion between the neck tool axis parallel portion and the neck taper portion provided behind the cutting edge portion is set to Ry 6.0 μm or less.
JP-A-10-225812 Japanese Patent Laid-Open No. 10-225813 JP 2002-11611 A JP 2002-66827 A

  By the way, in such a taper neck end mill, the cutting blade portion is inserted into the processing groove so that the outer peripheral surface of the taper neck portion is along the groove wall surface that is slightly inclined in the deep groove processing or the like. Cut the groove wall. However, a groove for discharging chips is formed in the cutting edge part, and the cross-sectional area thereof is reduced particularly on the outer peripheral side, and the rigidity of the cutting edge part tends to be impaired as compared with the neck part. .

  In this respect, in the taper neck end mill described in Patent Documents 1 and 2 in which the cutting edge portion itself is also tapered, the cross-sectional area and rigidity of the cutting edge portion increase toward the rear end side. Although bending is rare, the cutting edge shape is like a square blade, a ball blade, or a radius blade like the tapered neck end mill described in Patent Documents 3 and 4, and it rotates around its axis on its outer peripheral side. When the outer peripheral blade having a cylindrical shape with the locus centering on the axis is formed, the cutting blade portion itself is a boundary portion with the taper neck portion when trying to secure a certain groove depth for chip discharge. May cause bending. When the cutting edge portion is bent in this way, especially when the inclination of the groove wall surface of the processing groove is nearly vertical, the tip side portion of the tapered neck portion without the cutting edge or the boundary portion with the cutting edge portion is The groove wall surface may come into contact with the groove wall surface, and the end mill itself may be broken.

  Further, as in Patent Document 4, when a tool axis parallel part parallel to the tool axis (axis of the end mill body) is provided in the neck part behind the cutting edge part, the parallel part 1 as shown in FIG. Before the cutting blade 2 is formed, it is formed by cylindrical grinding integrally with the cutting blade 2, and then the cutting blade 2 is subjected to groove grinding and peripheral flank grinding to form the cutting blade 3. In this case, the outer diameter of the parallel portion 1 may be larger than the outer diameter of the cutting blade (outer peripheral blade) 3. 8, reference numeral 4 denotes an end mill body, reference numeral 5 denotes a neck taper portion, reference numeral 6 denotes a neck portion including the taper portion 5 and the parallel portion 1, and a broken line denotes a cutting blade before the cutting blade 3 is formed. The external shape of the part 2 is shown. Therefore, in such a taper neck end mill, when the cutting blade portion 2 is slightly bent, the stepped portion 7 between the parallel portion 1 and the cutting blade portion 2 comes into contact with the groove wall surface and the processing quality is impaired. Or end mill breakage.

  The present invention has been made under such a background, and in the tapered neck end mill having a cylindrical cutting edge whose rotation locus is parallel to the axis of the end mill body as described above, the cutting edge portion has a slight amount. An object of the present invention is to provide a tapered neck end mill that can prevent the end mill main body from coming into contact with the machining groove wall surface even if bending occurs, and can improve the machining quality and extend the end mill life.

  In order to solve the above-described problems and achieve such an object, the present invention provides a tip end portion of an end mill body rotated around an axis, and a rotational locus around the axis is formed in a cylindrical shape centered on the axis. A cutting blade portion having a cutting blade is formed, and a neck portion is formed on the rear end side of the cutting blade portion, and the neck portion is gradually tapered as the outer diameter increases toward the rear end side. And a parallel neck portion formed between the tapered neck portion and the cutting blade portion and having an outer diameter smaller than the outer diameter of the cutting blade and extending parallel to the axis. To do.

  Therefore, according to such a tapered neck end mill, a cutting blade portion having a cylindrical cutting blade whose rotation locus is centered on the axis, and a tapered neck portion whose outer diameter gradually increases toward the rear end side. A parallel neck portion is formed between the two, and although the parallel neck portion extends parallel to the axis, the outer diameter thereof is smaller than the outer diameter of the cutting blade. Even if bending occurs during cutting at a scarce cutting edge portion, the parallel neck portion can secure a distance from the groove wall surface, and the tip side of the neck portion can be prevented from contacting the groove wall surface. For this reason, it is possible to prevent the groove wall surface from being damaged by such contact, or to break the neck portion due to the resistance at the time of contact, thereby forming a high-quality processed groove wall surface and the end mill life. Can be extended.

  Further, when manufacturing such a tapered neck end mill, for example, a parallel neck portion is previously formed by cylindrical grinding or the like so as to be smaller than the outer diameter of the cutting edge, and then groove grinding and flank grinding are performed on the cutting edge portion. Therefore, the outer diameter of the parallel neck portion does not become larger than the outer diameter of the cutting blade as in the taper neck end mill described in Patent Document 4, so that the cutting edge can be formed reliably. It is possible to avoid contact with the groove wall surface. Here, if the boundary portion between the tapered neck portion and the parallel neck portion is formed so as to form a concave curve in the section along the axis, the outer diameter starts to increase from the parallel neck portion parallel to the axis. It is possible to prevent stress from concentrating on the boundary portion, and to prevent breakage from being easily generated from the boundary portion.

  The outer diameter of the parallel neck portion is preferably in the range of 0.85 × D to 0.95 × D with respect to the outer diameter D of the cutting blade. When bending occurs, it may not be possible to secure a sufficient space between the groove wall surface. On the other hand, if it is smaller than this, the parallel neck part itself will bend easily and the taper neck part will contact the groove wall surface. May occur. Further, if the length of the parallel neck portion in the axial direction is too long, the parallel neck portion is likely to be bent as in the case of the long neck end mill. On the other hand, if the length is too short, the taper neck portion is likely to contact the groove wall surface. Therefore, the length of the parallel neck portion is preferably in the range of 0.8 × D to 2 × D with respect to the outer diameter D of the cutting blade.

  1 to 3 show an embodiment of the present invention. In the present embodiment, the end mill main body 11 is integrally formed in a substantially cylindrical shaft shape centering on the axis O with a hard material such as cemented carbide, and the rear end side (right side in FIGS. 1 and 2) remains cylindrical. On the other hand, a cutting blade portion 13 is formed on the tip side (left side in FIGS. 1 and 2), and a neck portion 14 is formed between the cutting blade portion 13 and the shank portion 12, The shank portion 12 is held by the main shaft of the machine tool and is rotated in the end mill rotation direction T around the axis O and is fed in a direction intersecting the axis O, whereby the cutting blade portion 13 cuts a mold or the like. The material is subjected to cutting such as deep grooving.

  The cutting blade portion 13 is formed with a plurality of (two in this embodiment) chip discharge grooves 15 that are twisted toward the rear side in the end mill rotation direction T around the axis O from the front end toward the rear end. Cutting edges 16 are respectively formed on the outer peripheral side ridges of the wall surfaces of the chip discharge grooves 15 facing the end mill rotation direction T side. Here, the cutting edge 16 is located on the rear end side of the cutting edge portion 13, and the outer peripheral edge 17 having a rotation locus around the axis O forms a cylindrical shape centered on the axis O, and the tip of the outer peripheral edge 17. Continuing, in this embodiment, the rotation trajectory around the axis O is the cutting edge of a ball end mill formed from a bottom hemisphere 18 having a convex hemisphere centered on the axis O.

  Further, the neck portion 14 includes a parallel neck portion 19 that is continuous with the cutting edge portion 13 on the front end side, and a tapered neck portion 20 that is continuous with the shank portion 12 on the rear end side. Of these, the tapered neck portion 20 has a frustoconical shape centering on an axis O whose outer diameter is made equal to the parallel neck portion 19 at the tip and gradually increases at a constant rate toward the rear end. I am doing. However, the rate at which the outer diameter of the tapered neck portion 20 increases toward the rear end side is not so large, and in this embodiment, the inclination angle θ that the outer peripheral surface forms with respect to the axis O in the cross section along the axis O. The range is about 30 ′ to 5 °.

  In addition, the taper neck portion 20 has a rear end portion between the shank portion 12 and an inclination larger than the inclination angle θ with respect to the axis O as shown in FIGS. 1 and 2 in the present embodiment. A frustoconical connecting portion 21 whose outer diameter gradually increases toward the rear end side at the corner is formed, and the length of the end of the connecting portion 21 is the effective length of the tapered neck portion 20. Instead of the frustoconical connecting portion 21, the cross section along the axis O with the inclination angle gradually increasing toward the rear end may be a concave curved connecting portion.

  On the other hand, the parallel neck portion 19 is formed in a columnar shape extending along the axis O with the axis O as the center, and thus the outer diameter d is constant. And the outer diameter d of this parallel neck part 19 is made smaller than the outer diameter D of the cutting edge 16 of the said cutting edge part 13, ie, the outer diameter D of the cylinder which the outer peripheral edge 17 makes | forms in the said rotation locus | trajectory, In the embodiment, the range is 0.85 × D to 0.95 × D. Further, the length L of the parallel neck portion 19 in the direction of the axis O is in a range of 0.8 × D to 2 × D with respect to the outer diameter D of the cutting edge 16.

  In the present embodiment, the parallel neck portion 19 is formed so as to intersect at an angle at the tapered neck portion 20 and the boundary portion 22 in the cross section including the axis O as shown in FIG. In the boundary part 23 with the blade part 13, it connects with a level | step difference so that it may reverse | retreat to the inner peripheral side one step from the outer diameter D of the cutting edge 16 (outer peripheral edge 17). The core thickness (the diameter of a circle centering on the axis O that contacts the groove bottom surface of the chip discharge groove 15 in the cross section orthogonal to the axis O) up to the front of the rounded-up portion of the chip discharge groove 15 is constant. However, the cutting edge 6 is not formed in the neck portion 14.

  When the deep groove machining in the mold as described above is performed by the tapered neck end mill configured as described above, the end mill main body 11 is supported by the axis O vertically as shown in FIG. The cutting blade portion 13 is inserted into the processing groove while the outer peripheral surface of the tapered neck portion 20 is along the groove wall surface W of the processing groove slightly inclined with respect to the vertical direction. Cutting process. Here, in the cutting edge portion 13, the rotation locus of the cutting edge 16 (outer peripheral edge 17) is cylindrical, that is, the chip discharge groove 15 is formed where the outer diameter D is constant. Since the cross-sectional area is cut by the above, the rigidity is reduced, and in this embodiment, the outer diameter d of the parallel neck portion 19 is made smaller than the outer diameter D of the cutting blade 16, so that during the cutting process, By cutting the cutting edge 16 into the groove wall surface W, the cutting edge portion 13 and the parallel neck portion 19 are likely to bend as shown in FIG.

  However, in the tapered neck end mill having the above-described configuration, even when the cutting edge portion 13 and the parallel neck portion 19 are bent as described above, the outer diameter d of the parallel neck portion 19 is the cutting edge 16 in the cutting edge portion 13 as described above. Since the outer diameter D of the neck portion 14 is smaller than the parallel neck portion 19 of the neck portion 14 and the groove wall surface W, a sufficient space can be secured. Even when the angle θ is close to the angle θ, it is possible to prevent a situation in which the neck portion 14 comes into contact with the groove wall surface W to be damaged or the neck portion 14 is broken from the contacted portion. Become.

  In this regard, in the conventional tapered neck end mill, for example, the tapered neck end mill described in Patent Document 4, the outer diameter of the parallel portion 1 of the neck portion 6 connected to the cutting edge portion 2 is not made smaller than the outer diameter of the cutting edge 3. Rather, as shown in FIG. 8, the stepped portion 7 may be formed with a larger diameter than the outer diameter of the cutting edge 3. For this reason, if bending occurs in the cutting edge part 2 and the parallel part 1 as described above, a sufficient space cannot be secured between the groove wall surface W and the neck part 6 as shown in FIG. May come into contact with the groove wall surface W and damage the groove wall surface W to deteriorate its quality, or conversely, the load may concentrate on the portion of the neck portion 6 in contact with the groove wall surface W to cause breakage.

  In addition, since the outer diameter d of the parallel neck portion 19 is smaller than the outer diameter D of the cutting blade 16 in the cutting blade portion 13 in this way, in the tapered neck end mill having the above-described configuration, the cutting blade portion 13 includes the cutting blade 16. Before forming the cutting edge 16, the outer diameter d of the parallel neck portion 19 is formed to be smaller than the outer diameter D in advance, and then the cutting edge 16 is formed on the cutting edge portion 13 by groove grinding or outer peripheral flank grinding. Thus, even if the outer diameter D of the cutting blade 16 after grinding is smaller than the outer diameter of the cutting blade portion 13 before grinding indicated by a broken line in FIG. 3, the outer diameter d of the parallel neck portion 19 is smaller than the outer diameter D. Can be kept small. Therefore, since it is possible to more reliably prevent the neck portion 14 from contacting the groove wall surface W during the cutting process, the taper neck end mill having the above-described configuration is a deep groove having a high-quality groove wall surface W without scratches or the like. Can be formed on a work material such as a mold, and the end mill life can be extended to achieve economical cutting.

  However, if the outer diameter d of the parallel neck portion 19 is too small with respect to the outer diameter D of the cutting edge 16, the parallel neck portion 19 itself cannot withstand bending during cutting and can prevent breakage. There is a risk of disappearing. On the other hand, if the outer diameter d is too large and the difference from the outer diameter D becomes too small, it is not possible to ensure a distance from the groove wall surface W as in the tapered neck end mill described in Patent Document 4. Since there is a possibility, the outer diameter d of the parallel neck portion 19 is in the range of 0.85 × D to 0.95 × D with respect to the outer diameter D of the cutting edge 16 as in the present embodiment. desirable.

  Further, if the length L of the parallel neck portion 19 in the direction of the axis O is too long, the parallel neck portion 19 is liable to bend like the conventional long neck end mill, and in particular, the outer diameter of the parallel neck portion 19 is increased. In the tapered neck end mill having the above-described configuration in which d is smaller than the outer diameter D of the cutting edge 16, the parallel neck portion 19 may be broken. On the other hand, even if the length L of the parallel neck portion 19 is too short, the distance between the cutting blade portion 13 and the taper neck portion 20 on the rear end side of the neck portion 14 is reduced, and the cutting blade portion 13 and the parallel neck portion are reduced. Since the gap between the taper neck portion 20 and the groove wall surface W may not be sufficiently secured when the bending occurs in the 19, the length L is the cutting edge 16 as in the present embodiment. The outer diameter D is preferably in the range of 0.8 × D to 2 × D.

  In the present embodiment, the boundary portion 22 between the parallel neck portion 19 and the taper neck portion 20 in the neck portion 14 is formed so as to intersect at an angle in the cross section including the axis O, but the parallel neck portion 9 If the outer diameter d is made smaller than the outer diameter D of the cutting edge 16 and a sufficient space is ensured between the groove wall surface W when bending occurs, a modified example showing a rotation locus in FIG. As described above, the boundary portion 22 may be formed so as to be connected to the parallel neck portion 19 through a stepped portion whose diameter is reduced to the inner circumferential side at the tip of the tapered neck portion 20. However, in this case, when the parallel neck portion 19 is bent due to cutting resistance, there is a possibility that bending stress may concentrate on the boundary portion 22 thus formed in a step shape and cause breakage. As in the embodiment, it is desirable that the columnar parallel neck portion 19 is formed at the tip of the truncated cone-shaped tapered neck portion 20 so as to be connected to each other without causing a step difference by making the outer diameters d equal to each other.

  Further, in order to more effectively prevent breakage due to the concentration of bending stress, the boundary portion 22 between the tapered neck portion 20 and the parallel neck portion 19 is recessed in the cross section along the axis O as shown in FIG. It is more desirable to form a curved shape, particularly a concave curved shape such as an arc that smoothly contacts the parallel neck portion 19 and the taper neck portion 20, so that the bending when the parallel neck portion 19 is bent is formed. Stress can be distributed from the boundary 22 to its periphery. Note that the boundary portion 23 between the parallel neck portion 19 and the cutting edge portion 13 is also formed on the cutting edge portion 13 if it is formed in a concave curve shape that smoothly contacts at least the parallel neck portion 19 in the cross section along the axis O. Even when bending occurs, breakage from the boundary portion 23 due to stress concentration on the boundary portion 23 can be avoided.

  In the above embodiment, the ball end mill in which the rotation trajectory of the bottom blade 18 has a convex hemispherical shape has been described, but a square end mill in which the bottom blade 18 extends in a direction substantially perpendicular to the axis O and is substantially orthogonal to the outer peripheral blade 17 or the like. The present invention can also be applied to a radius end mill in which the bottom blade 18 and the outer peripheral blade 17 are connected via a substantially ¼ arc-shaped corner blade. That is, it is only necessary to form the cutting edge 16 (outer peripheral edge 17) in which the rotation locus around the axis O forms a cylindrical shape with the axis O as the center.

It is a side view which shows one Embodiment of this invention. It is a figure which shows the rotation locus | trajectory around the axis line O of embodiment shown in FIG. It is an enlarged view which shows the rotation locus | trajectory of the front end side part of the cutting blade part 13 and the neck part 14 of embodiment shown in FIG. It is a figure which shows the state when cutting the groove wall surface W of a work material by embodiment which showed the rotation locus | trajectory in FIG. It is a figure which shows the state when cutting the groove wall surface W of a cut material with the conventional taper neck end mill. It is a figure which shows the modification of embodiment which showed the rotation locus | trajectory in FIG. It is an enlarged view which shows the modification of embodiment which showed the rotation locus | trajectory in FIG. It is an enlarged view which shows the rotation locus | trajectory of the front end side part of the cutting blade part 2 and the parallel part 1 of the conventional taper neck end mill.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 End mill main body 13 Cutting edge part 14 Neck part 15 Chip discharge groove 16 Cutting edge 17 Peripheral blade 18 Bottom blade 19 Parallel neck part 20 Tapered neck part 22 Boundary part of the parallel neck part 19 and the taper neck part 23 Parallel neck part 19 and cutting Boundary part with the blade part 13 O Axis line of the end mill body 11 T Rotational direction at the time of cutting the end mill body 11 D Outer diameter of the cutting edge 6 (outer peripheral edge 17) d Outer diameter of the parallel neck part 19 L of the parallel neck part 19 Length in axis O direction

Claims (4)

  At the tip of the end mill body that rotates about the axis, a cutting blade is formed that has a cutting blade that has a cylindrical rotation centered around the axis. A neck portion is formed on the end side, and the neck portion is formed between a tapered neck portion whose outer diameter gradually increases toward the rear end side, and between the tapered neck portion and the cutting blade portion. A tapered neck end mill having an outer diameter smaller than the outer diameter of the neck and extending in parallel with the axis.   2. The tapered neck end mill according to claim 1, wherein a boundary portion between the tapered neck portion and the parallel neck portion has a concave curve shape in a cross section along the axis.   3. The outer diameter of the parallel neck portion is in a range of 0.85 × D to 0.95 × D with respect to the outer diameter D of the cutting blade. Taper neck end mill. The length in the axial direction of the parallel neck portion is in a range of 0.8 x D to 2 x D with respect to the outer diameter D of the cutting blade. The taper neck end mill according to any one of the above.

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